JP7264119B2 - Extreme ultraviolet light source device - Google Patents

Description

The present invention relates to an extreme ultraviolet light source device.

2. Description of the Related Art In recent years, along with miniaturization and high integration of semiconductor integrated circuits, the wavelength of light sources for exposure has been shortened. As a next-generation semiconductor exposure light source, an extreme ultraviolet light source device (hereinafter also referred to as an EUV light source device) that emits extreme ultraviolet light with a wavelength of 13.5 nm (hereinafter also referred to as EUV (Extreme Ultra Violet) light). Development is underway.
Several methods are known for generating EUV light (EUV radiation) in an EUV light source device. One of these methods is a method of generating high-temperature plasma by heating and exciting extreme ultraviolet radiation species (hereinafter also referred to as EUV radiation species), and extracting EUV light from the high-temperature plasma.

EUV light source devices employing such a method are classified into LPP (Laser Produced Plasma) type and DPP (Discharge Produced Plasma) type according to the high-temperature plasma generation method.
A DPP type EUV light source device applies a high voltage to a gap between electrodes supplied with a discharge gas containing EUV radiation species (gas-phase plasma raw material) to generate high-density high-temperature plasma by discharge. It utilizes the emitted extreme ultraviolet light. As a DPP method, for example, as described in Patent Document 1, a liquid high-temperature plasma raw material (for example, Sn (tin)) is supplied to the electrode surface that generates discharge, and a laser beam is applied to the raw material. A method has been proposed in which the material is vaporized by irradiating it with an energy beam such as a sintered material, and then a high-temperature plasma is generated by electric discharge. Such a method is sometimes called an LDP (Laser Assisted Discharge Plasma) method.

EUV light sources are used as light sources in lithographic apparatus in the manufacture of semiconductor devices. Alternatively, the EUV light source device is used as a light source device for a mask inspection device used in lithography. In other words, the EUV light source device is used as a light source device for another optical system device (utilizing device) that uses EUV light.
Since the EUV light is easily attenuated, the area from the plasma to the device using the EUV light is placed in a reduced pressure atmosphere, that is, in a vacuum environment.

On the other hand, debris is dissipated at high speed from the plasma generated by the LDP method. The debris includes tin particles, which are high-temperature plasma raw materials, and material particles of the discharge electrode that are slightly damaged by being irradiated with the energy beam. Debris is a hindrance to a utilization device, so a debris trap has been proposed that diverts the traveling direction of dispersed debris so that the debris does not enter the utilization device (Patent Document 1).

JP 2017-219698 A

Debris traps divide the space in which they are placed into smaller pieces with multiple foils, and work to lower the conductance and raise the pressure in that portion. Debris has a higher probability of collision in this area of increased pressure, so its velocity decreases and its traveling direction is diverted. Debris traps include fixed foil traps and rotating foil traps that deflect debris by colliding with it. A single apparatus may be provided with both a rotating foil trap and a stationary foil trap, or one or the other.
Debris whose progress is blocked by the debris trap accumulates in the debris container. Debris accumulation is more efficient when the debris is in the liquid phase, because if the debris is in the solid phase, the buildup will grow on certain points. Therefore, in order to heat the debris, it is desirable to provide heater wiring around the debris container.
However, when the heater wiring is arranged inside the enclosure under vacuum together with the debris container, it is difficult to inspect and repair the heater wiring. In addition, it takes time to replace the debris container in the housing and to remove debris such as tin from the debris container. In general, semiconductor manufacturing equipment is required to maximize the time (also referred to as uptime) available to users for product production activities. Therefore, it is necessary to shorten the time required for maintenance such as replacement of the debris container, and to lengthen the maintenance cycle as much as possible.

Therefore, the present invention provides an extreme ultraviolet light source device that facilitates inspection and repair of heater wiring that heats the debris storage container, facilitates replacement of the debris storage container, and facilitates removal of debris from the debris storage container. intended to provide

An extreme ultraviolet light source device according to an aspect of the present invention includes a light source unit that generates plasma that emits extreme ultraviolet light, a first vacuum housing in which the light source unit is arranged, and the extreme ultraviolet light is used. a second vacuum housing disposed between the utilization device and the first vacuum housing and communicating with the utilization device and the first vacuum housing; and a second vacuum housing disposed inside the second vacuum housing. a debris trap that diverts the traveling direction of debris dissipated from the plasma toward the utilization device; and a debris trap that is arranged outside the second vacuum enclosure and causes the debris whose traveling direction is diverted by the debris trap to fall. and a debris container. A wall of the second vacuum enclosure is formed with a through-hole that communicates the internal space of the debris container with the internal space of the second vacuum enclosure.

In this aspect, the debris whose traveling direction is diverted by the debris trap falls into the debris container through the through hole formed in the wall of the second vacuum enclosure. The debris container is arranged outside the second vacuum enclosure. Therefore, debris does not adhere to the heater wiring that heats the debris container, and inspection and repair of the heater wiring are easy. In addition, since the debris container can be easily removed from the second vacuum housing, it is easy to replace the debris container with a new debris container or to take out tin from the debris container.

In the aspect of the present invention, it is easy to inspect and repair the heater wiring that heats the debris container, and it is easy to replace the debris container or remove debris from the debris container.

1 is a schematic diagram showing an extreme ultraviolet light source device according to an embodiment of the present invention; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows a part of extreme-ultraviolet light source device which concerns on embodiment. It is a front view of a rotary foil trap of the extreme ultraviolet light source device according to the embodiment.

Embodiments according to the present invention will be described below with reference to the accompanying drawings. The drawings are not necessarily drawn to scale and some features may be exaggerated or omitted.

An extreme ultraviolet light source device (EUV light source device) 1 can be used as a light source device for a lithography device in semiconductor device manufacturing or a light source device for a mask inspection device used for lithography, for example, extreme ultraviolet light with a wavelength of 13.5 nm ( It is a device that emits EUV light).
The EUV light source device 1 according to the embodiment is an LDP-type EUV light source device. More specifically, the EUV light source device irradiates an energy beam such as a laser beam to a liquid-phase plasma raw material supplied to the surfaces of a pair of electrodes that generate discharge to vaporize the plasma raw material. A high-temperature plasma is generated by the discharge of EUV light is emitted from the plasma.

As shown in FIG. 1, the EUV light source device 1 has a chamber (first vacuum housing) 11 in which plasma is generated. The chamber 11 is made of a rigid body such as metal. The interior of chamber 11 is evacuated to suppress attenuation of EUV light.
The depiction of the interior of chamber 11 in FIG. 1 is a plan view of the interior of chamber 11 .

Inside the chamber 11, a light source unit 12 for generating plasma that emits extreme ultraviolet light is arranged. The light source section 12 has a pair of discharge electrodes 21a and 21b. The discharge electrodes 21a and 21b are discs of the same shape and size, the discharge electrode 21a being used as a cathode and the discharge electrode 21b being used as an anode. The discharge electrodes 21a and 21b are made of, for example, a high-melting-point metal such as tungsten, molybdenum, or tantalum.
The discharge electrodes 21a and 21b are arranged at positions spaced apart from each other, and the peripheral edge portions of the discharge electrodes 21a and 21b are close to each other. A discharge occurs in the gap between the cathode 21a and the anode 21b at the position where the peripheral edge of the cathode 21a and the peripheral edge of the anode 21b are closest to each other, thereby generating high-temperature plasma. Hereinafter, the gap between the cathode 21a and the anode 21b where the peripheral edge of the cathode 21a and the peripheral edge of the anode 21b are closest to each other is referred to as "discharge area D".

The cathode 21a is connected to a rotating shaft 23a of a motor 22a and rotates around the axis of the cathode 21a. The anode 21b is connected to the rotating shaft 23b of the motor 22b and rotates around the axis of the anode 21b. The motors 22a, 22b are arranged outside the chamber 11, and the rotary shafts 23a, 23b extend from the outside of the chamber 11 to the inside. The gap between the rotating shaft 23a and the wall of the chamber 11 is sealed with a sealing member such as a mechanical seal 24a, and the gap between the rotating shaft 23b and the wall of the chamber 11 is also sealed with a mechanical seal 24b. It is sealed with a sealing member such as The seal member allows rotation of the rotating shafts 23 a and 23 b while maintaining the reduced pressure atmosphere in the chamber 11 .
Thus, the discharge electrodes 21a, 21b are driven by separate motors 22a, 22b, respectively. Rotation of these motors 22 a and 22 b is controlled by the control section 15 .

Inside the chamber 11, a container 26a in which a liquid-phase plasma raw material 25a is stored and a container 26b in which a liquid-phase plasma raw material 25b is stored are arranged. Heated liquid phase plasma raw materials 25a and 25b are supplied to the containers 26a and 26b. The liquid-phase plasma raw materials 25a and 25b are, for example, tin (Sn).
The lower portion of the cathode 21a is immersed in the plasma raw material 25a inside the container 26a, and the lower portion of the anode 21b is immersed in the plasma raw material 25b inside the container 26b. Therefore, the plasma material adheres to the discharge electrodes 21a and 21b. As the discharge electrodes 21a and 21b rotate, the liquid-phase plasma raw materials 25a and 25b are transported to the discharge region D where high-temperature plasma is to be generated.

A laser (energy beam irradiation device) 28 is arranged outside the chamber 11 for irradiating an energy beam onto the plasma raw material 25a coated on the cathode 21a to vaporize the plasma raw material 25a. The laser 28 is, for example, a Nd: _YVO4 laser (Neodymium-doped Yttrium Orthovanadate laser) and emits an infrared laser beam L. However, the energy beam irradiation device may be a device that emits a beam other than a laser beam capable of vaporizing the plasma raw material 25a.
The irradiation timing of the laser beam by the laser 28 is controlled by the controller 15 .
An infrared laser beam L emitted from laser 28 is guided to movable mirror 31 . Between the laser 28 and the movable mirror 31 typically a light collecting means is arranged. The condensing means has, for example, a condensing lens 29 .

The infrared laser beam L is reflected by a movable mirror 31 arranged outside the chamber 11, passes through a transparent window 30 provided in the wall of the chamber 11, and reaches the outer peripheral surface of the cathode 21a near the discharge region D. be irradiated.
The axes of the discharge electrodes 21a and 21b are not parallel in order to facilitate the irradiation of the infrared laser beam L onto the outer peripheral surface of the cathode 21a. The interval between the rotating shafts 23a and 23b is narrow on the motor side and wide on the electrode side.
Anode 21 b is arranged between cathode 21 a and movable mirror 31 . In other words, the infrared laser beam L reflected by the movable mirror 31 reaches the outer peripheral surface of the cathode 21a after passing through the vicinity of the outer peripheral surface of the anode 21b. The anode 21b is retreated to the left side of FIG. 1 from the cathode 21a so as not to disturb the progress of the infrared laser beam L.
The liquid-phase plasma raw material 25 a coated on the outer peripheral surface of the cathode 21 a near the discharge region D is vaporized by the irradiation of the infrared laser beam L, and the gas-phase plasma raw material is generated in the discharge region D.

In order to generate high-temperature plasma in the discharge region D (to convert gas-phase plasma materials into plasma), the pulse power supply unit 35 supplies power to the cathode 21a and the anode 21b, and discharge is generated between the cathode 21a and the anode 21b. give rise to The pulse power supply unit 35 periodically supplies pulse power to the discharge electrodes 21a and 21b.
A pulsed power supply 35 is arranged outside the chamber 11 . A power supply line extending from the pulse power supply unit 35 passes through a sealing member 36 embedded in the wall of the chamber 11 to maintain a reduced pressure atmosphere in the chamber 11 and extends into the chamber 11 .

In this embodiment, two feeders extending from the pulse power supply 35 are connected to the containers 26a and 26b, respectively. The containers 26a, 26b are made of an electrically conductive material, and the plasma sources 25a, 25b inside the containers 26a, 26b are also an electrically conductive material, tin. Discharge electrodes 21a and 21b are immersed in the plasma raw materials 25a and 25b inside the containers 26a and 26b. Therefore, when the pulse power supply unit 35 supplies pulse power to the containers 26a and 26b, the pulse power is eventually supplied to the discharge electrodes 21a and 21b.
When a discharge is generated between the cathode 21a and the anode 21b, the gas phase plasma material in the discharge region D is heated and excited by a large current to generate high-temperature plasma. In addition, due to the high heat, the liquid-phase plasma raw material 25b coated on the outer peripheral surface of the anode 21b in the vicinity of the discharge region D is also turned into plasma.

EUV light E is emitted from the high-temperature plasma. The EUV light E is used in a utilization device 40 (lithography device or mask inspection device), which is another optical system device. A connection chamber (second vacuum housing) 42 is arranged between the chamber 11 and the utilization device 40 . The internal space of the connection chamber 42 communicates with the chamber 11 through a window 43 that is a through hole formed in the wall of the chamber 11 . Also, the connection chamber 42 communicates with the utilization device 40 . Only a portion of utilization device 40 is shown in the drawing.
As shown enlarged in FIG. 2 , a wall of the connection chamber 42 is formed with a window 44 that is a through hole, and the internal space of the connection chamber 42 communicates with the utilization device 40 through the window 44 . The interior of the connection chamber 42 is also evacuated to suppress attenuation of the EUV light E. EUV light E emitted from the plasma in the discharge region D is introduced into the utilization device 40 through windows 43 and 44 .

On the other hand, debris 46 is dissipated from the plasma at high speed. The debris 46 includes tin particles, which are high-temperature plasma raw materials, and material particles of the discharge electrodes 21a and 21b that are slightly damaged by being irradiated with the energy beam. When the debris 46 reaches the utilization device, it may damage or contaminate the reflective films of the optical elements in the utilization device and degrade performance. Therefore, a debris trap is provided in the connection chamber 42 to divert the traveling direction of the debris 46 so that the debris 46 does not enter the utilization device 40 . In this embodiment, the debris trap has a rotating foil trap 50 that also acts to collide with and deflect debris 46 . Although not shown, a stationary foil trap may be provided in connection chamber 42 .

The rotary foil trap 50 has the configuration disclosed in Patent Document 1. Specifically, as shown in FIGS. 2 and 3, the rotatable foil trap 50 includes a central hub 51 , an outer ring 52 concentric with the hub 51 , and a number of hubs 51 and 52 positioned between the hub 51 and the outer ring 52 . It has a foil 53 . Each foil 53 is a thin film or thin plate. The foils 53 are radially arranged at equal angular intervals. Each wheel 53 lies on a plane containing the central axis of hub 51 . The material of the rotating foil trap 50 is a refractory metal such as tungsten and/or molybdenum.
The hub 51 is connected to a rotating shaft 55 of a motor (rotary drive device) 54 , and the center axis of the hub 51 matches the center axis of the rotating shaft 55 . The axis of rotation 55 can be regarded as the axis of rotation of the rotary foil trap 50 . Driven by motor 54 , rotating foil trap 50 rotates and rotating foil 53 collides with incoming debris 46 to prevent debris 46 from entering utilization device 40 .
The rotating foil trap 50 is arranged inside the connection chamber 42 while the motor 54 is arranged outside the connection chamber 42 . A wall of the connection chamber 42 is formed with a through hole 56 through which the rotating shaft 55 passes. A gap between the rotating shaft 55 and the wall of the connection chamber 42 is sealed with a sealing member such as a mechanical seal 57, for example.

Since radiant heat of the plasma is applied to the rotary foil trap 50, in order to prevent overheating, the rotating shaft 55 may be made hollow to allow cooling water to flow therethrough for cooling. A water cooling pipe 59 is wound around the motor 54 to prevent overheating due to the operation of the motor 54 itself. Water flows through the water-cooling pipe 59 and takes heat from the motor 54 through heat exchange.
A heat shield plate 60 is arranged in the connection chamber 42 to prevent the rotary foil trap 50 and the motor 54 from overheating. The material of the heat shield 60 is a high melting point metal such as tungsten and/or molybdenum. A heat shield 60 is interposed between the plasma and the rotating foil trap 50 . A through hole 60 a is formed in the heat shield plate 60 . The through hole 60a is positioned intermediate the window 44 and the plasma.
EUV light E is emitted from the plasma in various directions. Part of the EUV light E passes through the window 43 of the chamber 11, the through hole 60a of the heat shield plate 60, the gaps between the plurality of foils 53 of the rotary foil trap 50, and the window 44, and is introduced into the utilization device 40. . The plurality of foils 53 of the rotating foil trap 50 are arranged parallel to the optical axis of the EUV light E traveling towards the window 44 so as not to block the EUV light E traveling towards the window 44 .

In this embodiment, a motor 54 for rotating the rotating foil trap 50 is arranged outside the connection chamber 42 in which the rotating foil trap 50 resides. Therefore, inspection and repair of the motor 54, the wiring 54a, 54b of the motor 54, and the water cooling pipe 59 are easy. In addition, since the wirings 54a and 54b of the motor 54 and the water cooling pipe 59 are arranged outside the connection chamber 42, there are fewer sealing points in the connection chamber 42 than in the case where they are arranged inside the connection chamber 42. Furthermore, since the motor 54 is arranged outside the connection chamber 42, the motor 54 can be easily cooled.

Debris 46 is emitted from the plasma in various directions together with the EUV light. A portion of debris 46 enters connection chamber 42 through window 43 of chamber 11 . A debris container 64 into which debris 46 falls is arranged below the connection chamber 42 . Some of the debris 46 that has entered the connection chamber 42 deposits on the heat shield 60 . They are melted by radiant heat from the plasma, and when they reach a certain amount, they gather under the shielding plate 60 due to gravity and drop into the debris container 64 as droplets. Part of the debris 46 that has entered the connection chamber 42 and tin that has spilled from the discharge electrodes 21a and 21b and the containers 26a and 26b are guided to a receiving plate 65 heated by a heater installed in the connection chamber 42 and contained therein. It drops into container 64 . The debris 46 that has entered the connection chamber 42 and passed through the through hole 60 a of the heat shield plate 60 changes its traveling direction by being bounced by the foil 53 of the rotary foil trap 50 and falls into the debris container 64 .
A debris container 64 is arranged outside the connection chamber 42 . A through hole 66 is formed in the bottom wall of the connection chamber 42 to communicate the internal space of the debris container 64 and the internal space of the connection chamber 42 . The debris container 64 has a flange 64A on its top. The opening of the debris container 64 surrounded by a flange 64A overlaps the through-hole 66, and the flange 64A is fixed to the bottom wall of the connection chamber 42 with screws, for example. A gap between the flange 64A and the bottom wall of the connection chamber 42 is sealed by a gasket 68 provided there.

Since most of the debris 46 is tin, the debris containment vessel 64 can also be referred to as a tin collection vessel. A heater wire 69 for heating the debris container 64 is wound around the debris container 64 . During use of the EUV light source device 1, the heater wiring 69 heats the interior of the debris container 64 to the melting point of tin (approximately 232° C.) or higher, and the tin accumulated inside the debris container 64 is brought into a liquid phase. there is The reason why the tin inside the debris storage container 64 is in the liquid phase is that when the solid debris 46 accumulates, the accumulated matter grows at a point where the debris 46 tends to fall, just like a stalagmite in a limestone cave. Because it is going. As a debris buildup grows on a particular point, the buildup at a few points contacts the rotating foil trap 50 and prevents rotation of the rotating foil trap 50, while less debris accumulates at other points. or damage the rotary foil trap 50. Alternatively, accumulations may reach the optical path of the EUV light E traveling toward the window 44 and block the EUV light E. By liquidizing the tin inside the debris container 64, the upper portion of the accumulated tin is flattened.
When collecting the tin accumulated in the debris container 64, the inside of the connection chamber 42 is returned to the atmospheric pressure, and the heating by the heater wiring 69 is stopped. Then, after the debris storage container 64 returns to normal temperature, the debris storage container 64 is removed from the connection chamber 42 and a new debris storage container 64 (not filled with tin) is attached to the connection chamber 42 .
The tin inside the debris container 64 removed from the connection chamber 42 is in a solid phase, but can be removed from the debris container 64 by reheating, so the debris container 64 can be reused.

In this embodiment, the debris 46 deflected by the rotary foil trap 50 falls through a through hole 66 formed in the wall of the connecting chamber 42 into a debris container 64 . A debris container 64 is arranged outside the connection chamber 42 . Therefore, the debris 46 does not adhere to the heater wiring 69 that heats the debris container 64, and inspection and repair of the heater wiring 69 are easy. In addition, since the debris storage container 64 can be easily removed from the connection chamber 42 , it is easy to replace the debris storage container 64 with a new debris storage container 64 or take out tin from the debris storage container 64 .

Furthermore, a monitoring device 70 for monitoring the EUV light E is arranged outside the connection chamber 42 . The monitoring device 70 is a detector that detects the presence of the EUV light E or a measuring instrument that measures the intensity of the EUV light E. FIG.
The wall of the connection chamber 42 is formed with an extreme ultraviolet light guide hole 71 that is a through hole through which the EUV light E passes. A tube 72 is provided to pass through.

A through hole 60b is formed in the heat shield plate 60, and a monitoring device 70, an extreme ultraviolet light guide hole 71 and a tube 72 are arranged on an extension of a straight line connecting the plasma and the through hole 60b. Therefore, a part of the EUV light E emitted from the plasma reaches the window 43 of the chamber 11, the through hole 60b of the heat shield plate 60, the gaps between the plurality of foils 53 of the rotating foil trap 50, the edge of the wall of the connection chamber 42, and the It passes through the ultraviolet light guide hole 71 and the lumen of the tube 72 to reach the monitoring device 70 .
In this way, the EUV light E can be monitored by the monitoring device 70. FIG. Since the monitoring device 70 is arranged outside the connection chamber 42, it is easier to inspect and repair the monitoring device 70 and the wiring 70a, 70b of the monitoring device 70 than if it were arranged inside the connection chamber 42. In addition, since the wirings 70a and 70b of the monitoring device 70 are arranged outside the connection chamber 42, there are fewer sealing points in the connection chamber 42 than when they are arranged inside the connection chamber 42. FIG. Furthermore, since the monitoring device 70 is arranged outside the connection chamber 42, overheating of the monitoring device 70 can be suppressed.

Although the invention has been illustrated and described with reference to preferred embodiments thereof, it will be appreciated by those skilled in the art that changes in form and detail can be made without departing from the scope of the invention as set forth in the claims. One thing will be understood. Such changes, alterations and modifications are intended to fall within the scope of the present invention.

1 extreme ultraviolet light source device (EUV light source device)
11 chamber (first vacuum enclosure)
12 light source units 21a, 21b discharge electrode 40 utilization device 42 connection chamber (second vacuum housing)
43, 44 windows 46 debris 50 rotating foil trap (debris trap)
52 outer ring 54 motor (rotation drive device)
54a, 54b Wiring 55 Rotating shaft 56 Through hole 57 Mechanical seal 59 Water cooling pipe 60 Heat shield plate 64 Debris container 66 Through hole 69 Heater wiring 70 Monitoring device 70a, 70b Wiring 71 Extreme ultraviolet light guide hole 72 Pipe

Claims (2)

a light source unit that generates plasma that emits extreme ultraviolet light;
a first vacuum housing in which the light source unit is arranged;
a second vacuum housing disposed between the utilization device using the extreme ultraviolet light and the first vacuum housing and communicating with the utilization device and the first vacuum housing;
a debris trap disposed inside the second vacuum enclosure for diverting the direction of travel of debris dissipated from the plasma toward the utilization device;
a debris storage container disposed outside the second vacuum housing, into which debris whose traveling direction is deflected by the debris trap falls ;
a receiving plate disposed inside the second vacuum enclosure for receiving part of the debris that has entered the inside of the second vacuum enclosure;
The bottom wall of the second vacuum enclosure is formed with a through hole that communicates the internal space of the debris container with the internal space of the second vacuum enclosure. Debris falls from the inside through the through hole into the debris container, and debris received by the receiving plate is guided by the receiving plate and drops into the debris container. An extreme ultraviolet light source device characterized by: The bottom wall of the second vacuum enclosure has a portion that is not covered with the backing plate, and the top surface of the portion is inclined so as to become lower as it approaches the through hole. The extreme ultraviolet light source device according to claim 1, characterized in that:

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